Propeller



K. F. l. KIRSTEN.

PROPELLER.

APPLICATION FILED DEC,1, 1921.

Patented Oct. Y?, 1922.

l1 SHEETS-SHEEI l.

all M ITV /0 4 f m n s 2 2 25 f im I 2 n 6 H 5M K IW J J El ,f W .H K lv 5 .rv 3% Mv m 0.23 a f/ /K y 2 m., 3 i. i 3l |H SWU 7, /1 w Md IA 7 2 9 /7 2 2 3f ,A Z 3 4 Wd Z fm 3 2 3 5 2 J 2 Z 4 2 f www@ K. F. J. KIRSTEN.

PROPELLER.

APPLICATION FILED DEI:l I. 1921.

1.432,70@ Patented Oct. l?, 1922.

'Il SHEETS-SHEET 2.

LQSQHU@ Panted oct. 17,1922

Il SHEETS-SHEET 3.

ATTORNEY g Patented Oat. E7, 11922@ ll SHEETSw-SHEET 4.

ATTORNY K. F. KIRSTEN.

PROPELLER. Q APPLICATION mso DEc,1.1921.

LSQGG. Patented @en 3179 1922 ll SHEETS-SHEET 5.

INVENTOR /10/7 FJ. Kms/Lef?.

ATTORNEY K. F11. KIRSTEN.

PROPELLER.

APPLICATION man om I. 1921.

ASQ.,

f?, .za

ATTORNEY K. F. J. KIRSTEN.

PROPELLER.

APPLICATION man DEc,1,1921.

Patent-ed Oct. E7, 1922.

Il SHEETS-SHEET JEL--- l ATTORNEY- K. F. J. KIRSTEN.

PROPELLER.

APPucATroN man nEc.1. 1921.

LQBQJQQ, Paname@ 001;. 17, 1922.-

H SHEETS-SHEET 8.

f2@ Jg Q ATTORNEY K. F. l. KIRSTEN.

PRGPELLER.

APPLICATloN FILED Dc,r1,1921.

1,432,79@ I Patented Oct. M, 19221 ATTORNEY p' K. F. 1. KIRSTEN.

PROPELLER.

APPLICATION FILED DEC.I,1921. I QO. y Patented Oct. 17, 1922.

INVENTOR /Q/f FJ /1//71576/7. BY l l f ATTORNEY K. F. I. KIRSTEN.

PROPELLER.

APPLICATION FILED DEC. I, 192i. 1,432,70, Patented oct-.17,1922

/ 1l SHEETS-SHEET II- u Rig' J5. lNvENToR JL, ATTORNEY Patented @et l?, 1922.

STATES KURT F. J'. KIRSTEN, OF SEATTLE, WASHINGTON, ASSIGNOR OF ONE-HALF TO WILLIAM E. BOEING, 0F SEATTLE, WASHINGTON.

PROPELLER.

Application led December 1, 1921. Serial No. 519,247.

To all whom t may concern.'

y Be it known that I, KURT F. J. KiRsTEN, a citizen of the United States, residing at Seattle, in the county of King and State of lrVashington, have invented a certain new and useful Propeller, of which the following is a specification.

My invention relates to the art of propellers, and more particularly my invention relates to propellers of the type embodying a plurality of vane or blade members mounted so as to rotate upon their ownaxes while simultaneously the axes of said blades themselves rotate about a common aXis,-said axis being at right angles to the direction of the fluid medium through the propeller.

The scope of attempted application of such type of propellers divides itself into two fields: first: water wheels and windmills, that is, instances where the energy is transferred from the fluid medium to the propeller (motor operation); and second, marine and aerial propellers-that is, instances where the propeller transmits energy to the fiuid medium (generator operation).

In defining my invention, I will describe the same as applied to the problems peculiar to aerial propellers and aerial navigation, but be it noted that the application of m invention is not to be so limited; and a though the same principles apply throughout both fields and to both the air and water mechanisms in each of such fields, nevertheless the supreme test occurs in the field of vaerial navigation, wherein highly efficient operation even to be in any degree practicall operative (i. e. achieve flight) presents pro leinsiiot otherwise encountered.

Respecting the prior art, the accepted and approved propeller inthe field of aerial navigation, as is well known, is of the screw design, which has the axis of rotation coinciding with the direction of the fluid medium through the propeller. 4 Such screw propellers for aeroplanes present most intricate problems in design, manufacture, and operation. The designer must know the weight, parasite resistance, engine speed and the desired normal traveling speed of the machine before he can proceed with his propeller'design. His work is largely based upon empirical formulae and when his design is finished he cannot guarantee the performance of the propeller to be within the range of performance guarantees usually given withother industrial machinery. As the art is developed to the present day, two independent designsv would furnish two widely varying propeller foims for the same given performance and it can also be said that propellers designed by the most capable engineers must almost in all cases be modified after a trial performance. It is important to note that for best performance of a given aeroplane, this plane must be supplied with its own particularly designed propeller and that no propeller of'another machine of different type can operate as efficiently unless the weight, parasite resistance, engine speed and normal traveling speed happen to be the same.

Propeller design is perhaps the only branch of engineering design where the factor of safety is allowed to be omitted, although public safety is vitally involved in aeronautics as well as in other branches. The margin of safety adopted approximates only about ten ,per cent and in operation this margin is often greatly reduced, whereas in other branches this margin is usually 400%. In order to offset this leniency in favor of the manufacturer to most exacting specifications. 4

The extreme stresses to which the prope-ller is subjected gives rise to manufacturing difficulties of large roportions. The selection of woods as to kinds is reduced by the element of quantity production to very small limits for efficiently operating propellers and as only the small portion of most select quality is permitted to be used, the bare cost of raw material is excessively high.

the designer, purchasers, private or overnmental, attempt to avoid latent de ects in materials and workmanship by subjecting 85 I.

The preparation of said material in drying and tempering to insure uniformity is likewise expensive. The construction process includes some seventeen distinct operations as follows: (1) surfacing boards to proper thickness and tooth planing surface, (2) cutting laminae, (3) ballancing laminae, (4) tempering laminae, (5) gluing laminas,

(6) conditioning glued laminae, (7) ioiigh- 105 ing out of propeller, (S) reconditioning of propeller, (9) final working of propeller. (10) balancing of propeller, (11) covering with fabric, (12) aluminum leafing, (13) metal tipping, (14) enameling, (15) final 110 orately prepared product; Its value must blade.

be measured by the effectiveness of, .the length of, and the safety factor in the service rendered. The design determines the original effectiveness, but service conditions mayv decrease same quickly. Onefhght under average conditions is sometimes sufcient to make further service inefficient and unadvisable. The great speed at which the resent direct connected air screw operates is a major factor in shortening its service life, and making it hazardous. A standard Liberty propeller, nine feet in diameter and revolving at normal engine speed of. 1700 R. P. M. has a tip speed of 545 M. P. H. In service, the propeller must function while the airplane is on ground, on the water or inthe air. Thus, the propeller is a constant source of danger to those who come in cont y y tion belongs, 'have been most often aptact with its operations, even though the same are under favorable conditions. Sand,

water-spray, wet or dry grass, rough ground,

rain, snow, hail, severe heat and cold are enemies of the propeller 1n service. For example, so great is the impact that even water in the form of raindrops impinging upon a blade during flight cuts away the advancing edge above the' metal tipping, and pits the Moreover, said high rotational velocity produces a deafening roar which ren- 1 ders communication between operators practically impossible and this presents a situation fraught with great danger on oc-.`x casions of emergency.

Thus, as respects designing, low per cent of efliciency, small margin of safety, high rotational velocity, high cost, involved manufacturing processes, and short service life, there are most serious objections lto standard aeroplane propellers. Furthermore, there are objections more fundamental, namely, the development of lifting forces by merely imparting to aerofoils rapid motion of translation involves great loss of energy and difficulties incident to arising from and alighting upon the ground. Finally, such method of flight is most seriously objectionable on account of the manylimitations attendant upon maneuvering of the machine, for instance, the inability to maintain at will the machine in a fixed position over the earth.

Such are the objections tothe screw type of the specific design or type to which my invention belongs, be it noted that so far as known, no propeller of this type has ever been designed capable of developing sufficient power to be of practical value in aerodynamics if, indeed, in any field of use. The existence. of said type seems confined to the realm of the paper art. In the practical field offiying, the great desideratum is that a propeller be able to rovide sufficient lifting force per unit of)- power applied and weight involved. Obviously, a propeller lacking in this requisite is aerodynamically and so far as being' of service to mankind, no propeller at all. As will appear more clearly below, it is submitted that the difficulty in such type of propeller herein in question and as to heretofore designed has not been superficial, has not been. due to av mere lack of strength of materials, but has been fundamental and has related directly to the law or principle of the device.

Propellers of the type to which my invensaid vane on revolving. There are instances' where several times this number of vanes havebeen provided but without any reference to the significance of the proportion of the width of the vane to the diameter of the orbit described by the axis of the vane. Theoretical and scientific analysis and eX- perimentation has shown me that such construction will develop forces in exactly the opposite direction to that intended and will thereby create a condition which prevents the development of utilizable forces. Sails, i. e., frames having panels of canvas, have been suggested in the prior art, but these are inoperative as demonstrated hereinafter.

In general, the object of my invention is to overcome these objections and provide a propeller of the type in question characterized by being most efficient or free from self-produced counteracting forces in operation and being capable of practical use in fields of operation requiring the greatest degree of refinement. A primary object of my invention is to provlde a propeller of said type which will develop as a generator maximum power in proportion to its size and weight and which will transmit, as a motor, maximum power. Another primary object of my invention is to provide such a propeller embodying blades (I prefer to call my vane members blades for their narrowness and rigidity render such a term most apt), the width of which is so related to the diameter of the orbit described by the axes of the blades in rotating about the common axis that the angle of incidence, between said blade and the direction of its movement through the fluid medium with which said blade interactsis uniformly upon a given sidel of the blade cord. Also, a primary object is to provide such' a propeller whose blades have the relationship to the orbital diameter next above described so that said angle of incidence is practically constant in magnitude at all points along the blade cord at all times with a given rate of orbital rotation. Further, a primary object is to provide such a propeller whose blades have said relationship to the orbital diameter so that the direction of the effective working forces developed by each blade approximately focus in part upon, and approximately radiate in part from, a common axis or center. Another primary object is to provide such a propeller of the type in question such that all the blades may be used to develop utilizable forces in all the several positions (save one only and then only momentarily) about the common axis of rotation. A further object is to provide a blade of such charcater that it can be positively designed for propeller urposes to achieve a definite performance rom available aerodynamical data 'calculated and tested for Wing sections. i Still another primary object is to provide a propeller of the type in question which will receive and discharge the fluid stream practically unin` terrupted by the development of burbling or eddying currents in the stream as it passes through the propeller. Still another primary object is to provide a propeller' of the type in question whose blades have the said relationship to the orbital diameter, so that the velocity of the Huid stream developed when-the propeller is operated as a generator, that is to impart energy to the fluid medium, will be less in magnitude by only a smalldegree as it passes through the propeller than the rotational velocity of the propeller, whether said velocity be great or small; and when the propeller is operated as a motor, that is, to receive energy from the fluid medium, that its rotational velocity1 will be less in magnitude, by only a small degree, than the velocity of the fluid streamal whether said velocity be great or small.

Another primary object is to provide such type of propeller with a blade which has surfaces of a contour which conforms to the eccentricity requirements. Again, a primary object is to provide a propeller having such number of blades that it will develop maximum lift per unit of power applied wherein the providing of ap between the blades is essential to supp y the necessary fluid vbody against which the blades may exert their thrust. Finally, the purpose of my invention is the conversion of rotary motion into motion of translation or vice versa by means of blades moving in an orbit about a common axis with their cords disposed in such a way as to provide for most desirable interaction between the blade and the impinging fluid medium from which or to which, respectively, it is to receive or impart energy.

In general, I attain these obects by providing a propeller of the type in question with blades the width of which bear a relationship to the diameter' of the orbit described by the axes of the blades in rotating about a common axis so that the angle of incidence is uniformly, i. e., at all times, disposed on the side of theblade against which the fluid medium impinges and is practically constant in magnitude. The 95 said relationship ofthe width of the blades and the diameter of said orbit, together with all the incidents that flow therefrom, constitutes, in fact, the' law or principle of the machine embodying my invention. Also 100 closely associated with my means of obtaining the above objects is the form of the blade and the provision for the number of blades to satisfy the relationship of gap.

The above mentioned general objects of loav my invention together with others inherent in the same are attained by the mechanism illustrated in the following drawings, the same being merely preferred exemplary forms of embodiment of my invention, throughout which drawings like reference numerals indicate like parts: l N

AFig. l is a view in section of a propellerl embodying my invention;

fFig. 2 1s a view on dotted line 2, 2 of 115 Fig. l;

Fig. 3 is a view in cross-section of a blade. of preferred form for said device;

Fig. 4 is a side view in elevation of a propeller embodying my invention;

Fig. 5 'is an end view in elevation of the same;

Fig. 6 is a View in elevation in partand in section in part of a blade of a modified form;

IFig. 7 is an end view of a modified form of a propeller embodying my invention wherein a chain-drive mechanism is substituted. for gear mechanism;

Fig. 8 is a diagrammatic view illustrating 130 graphically the velocity of the axis of each blade insuccessive positions while rotatlng about a common axis when the velocity ot' translatioi'is equal to that of rotation of the axes about said common axis, said velocities being represented both in magnitude and direction;

Fig. 9 is a diagrammatic view illustrating graphically the velocity of the axis of each blade in successive positions while rotating about acommon axis when the velocity of rotation is fifty per cent greater than that of translation.

Fig. 10 is a diagrammatic view illustrating graphically' the resulting forces pro- -duced by the interaction of the blades and the fluid medium (said resulting forces being the resultant of the forces designated aerodynamically as lift and drag" forces) Fig. 11 is a diagrammatic View illustrating` graphically the resulting forces produced when the axis of symmetry forms an angle beta w'ith a line at right angles to the direction of the movement of the propeller in the fluid medium;

Fig. 12 is a diagrammatic view illustrating graphically the resulting velocities when the peripheral velocity of the axes of the blades is fifty per cent less than the velocity of translation of the fluid medium;

Fig. 13 is a diagrammatic view illustrating graphicallythe resulting forces developed when the peripheral velocity of the axes of the blades is fifty per cent less than the velocity of translation of the fluid medium; and

Figs. 14 and 15 (same being complementary to each other) are diagrammatic views representing graphically the derivation of the proper ratio of blade width to orbital diameter, as well as the basis of thepreferred form of blade.

Two round disks 17 and 18 (Fig. 1) are united by means of a hub 19 to form a cylindrical frame, rotatively mounted upon a shaft 20` said disks having a plurality of blades 21, 16 being shown herein for'illustration (Fig. 2) revolvably mounted between said disks, and at equal intervals about the periphery of said disks. In the inner face of disk 18, a master gear 22 is provided which intermeshes with gears 23 mounted u )on the axles 24 of the blades. Four blades (h ig. 5) positioned at ninety degrees apart are also each provided with a bevel gear 25 which intermeshes 'with a -bevel gear 26 on shaft 27, which in turn has a bevel gear 28 disposed to intermesh with bevel gear 29 revolvably mounted upon shaft 20, the center of which constitutes the axis 30 of the propeller as a whole or the common axis of rotation of the axes of the blades of the propeller. A thrust ball bearing 31 supports the weight of the propeller while a radial plane which are yball bearing 32 is also provided to maintain Ithe propeller radially disposed upon the lsleeve 34 being an extension of hub 19 carries a pulley 35. A cover 36 of stream line design or form is provided for each disk 17 and 18 and a control lever37 is provided for bevel gear 29, whereby the angular position of the blades as respects each other may be changed, i. e. the axis of symmetry to be described below may be changed or held in a given position. The gear ratio is such that the blades are caused to rotate upon their own axes with one-half t-he velocity of said axes about the common axis 30, i. e. said means simultaneously causes the number of rotations of the blades on their axes to be egual to one half the number of revolutions o the blades in their orbit about said common axis.

Obviously, the blades successively occupy the same ositions and for purposes of illustration Cpositions are chosen,

1g. 2) sixteen one for each blade, an said positions are designated by roman numerals I to XVI inelusive. The blade in position I is mounted with the cord 38 of the blade at right angles to the diameter of the propeller passing through the axis of the blade. By the cord of the blade is meant the straight line passing through the longitudinal axis of the blade and joining the edges of the blade, or it may be defined as the transverse axis of the blade, i. e. the line of the blade with respect to which the blade is conversely symmetrical. The blade in position IX is mounted with its cord coincinding with the diameter of the propeller, which, in other words, makes said cord at right angles to the cord of the blade in position I. The blades in all the remaining positions are mounted with their, cords respectively trained upon the longitudinal axis of the blade in position I, that is, the projections of the cords pass through the said axis of the blade in position I.

Manifestly, the cords of the blades in positions II to VIII inclusive on the left hand side of that plane coincinding with the cord of the blade in position IX, the axis 30, and the longitudinal axis of the blade in position I, form angles respectively with said equal to the angles formed bythe cords of the blades oppositely disposed on the right hand side of said plane, that is, of blades in positions X to XVI, inclusive. Any two blades similarly positioned as respects this lane, such as blades in positions II and X 7I, constitute a pair of blades. The line 39--40 of intersection of this said plane with any plane through the blades at right angles to the axis 30, i. e. between the disks or in short intermedithe shaft 20 by means ate the length of the blades,'is herein called the axis of symmetry of the blades.

In the modified form shown in Fig. 7, a chain driving mechanism is substituted for the gear driving mechanism, said chain driving mechanism consisting of an endless chain 41, which engages sprocket wheels 42 fixedly mounted on the hub of each blade. Two of the blades positioned one hundred eighty degrees apart are also provided with sprocket wheels 43 and 44. Secured to the shaft 20 is a double sprocket wheel 45 over which drive chains 46 and 47 pass to sprocket wheels 43 and 44 respectively. The ratio between the sprocket wheels 44 and 45 is such that the blades turn upon their own axes with onehalf the velocity with which they revolve about the common axis 30 precisely as hereinabove described in connection with the gear driving mechanism.

In operation as a generator, power from any suitable source may be transmitted to the propeller through the pulley 35 which will cause the frame composed of the disks l17 and 18 to revolve. Since the bevel gear 29 is normally held stationary in relation to of control lever 37, a rotary motion will be imparted to each bevel gear 25 through the means of shaft 27 and bevel gear 26. The velocity of rotation of the blades is to the velocity of rotation of the axes about the common axis as one is to two as above set forth, so that the propeller will revolve twice before a given side of a blade resumes the same position in space. This establishes the condition of mechanical symmetry of the blade cords. The operation of the device as a motor embodying my invention is the reverse of that described for the device` operatin as a generator. The kinetic energy of te fluid medium transferred to the propeller by impinging upon the blades causes the propeller to revolve and the power developed may be withdrawn through the means of disks 17 and 18, besides forming a cylindrical frame,

peller for the fluid stream through the propeller, whreby laterally directed interference with said stream is avoided and impingement upon the blades on the outlet side of the propeller may be controlled more delinitely. VVhile in this wise. the` said end walls, in general, assist in providing for the best operation of the propeller, more par ticularly there are instances wheresaid end walls are most important, such as where the particular application of the propeller may require a high degree of interrupting, breaking up or slowing up of the stream of the fluld medium through the propeller, as for example where it is required to function, not only as amfere propeller (either operating as a motor or generator), but to afford the pulley 35. The b function as channel-forming or fluid-medium confining end walls of the proprotection asa parachute in aerial navigation in the event of an accident tothe engine or power transmission or the like. The said disks may be dispensed with where no such functions as indicated are required, and any equivalent conventional frame may be employed. The stream-line cover 36 not only functions to protectr the mechanism enclosed against inju and render more easy the displacement o the fluid medium as the propeller moves through the same, but also serves as a guard against the throwing off of parts which may become loosened by operation. Obviously a cover alone and of any form secured to any conventional open cylindrical wheel frame (i. e., Without disks) will serve the function of an end wall for the propeller. ation. v

The mode of operation of a device embodying my invention and the principle thereof will next be more fully set forth and explained in an analysis of the forces developed by the blades due to their interaction with the fluid medium arising by reason of the three velocities to 'which the blades are subject, said velocities being: (1) the velocity of the fluid medium through the propeller, i. e. the translationall velocity'Vt; -(2) the velocity of rotation of the axes of the blades in their orbit upon the common axis, i. e. the rotational or peripheral velocity, Vp and (3) the velocity of turning of the blades upon their own axes, i. e. the satellite ve- Vs.A Said analysis will set forth graphically the direc-tion and magnitude of Such is the mechanical opersaid forces produced, together with the new discoveries pertaining to the operation of the blades, and will develop both the difliculties lto be overcome and the conditions essential for the cooperation and control of said forces in an utilizable mechanical embodiment.l

In Fig. 8, the translational velocity Vt, eing shown asa horizontal line, is assumed to be equal to the peripheral velocity VD, being shown as the tangent to the orbit of movement of theaxisof Heach blade while rotating about the common axis 30. Manifestly, Ithe relative velocity of movement of each blade and the medium may be found by geometrically combining in vectorial form these two velocities, the resulting absolute velocity (Vr) off the blade in the fluid medium bein the diagonal of the parallelogram, of w ich the above velocities form the sides. lIt is seen on the drawing that the velocity, or relative velocity, of the blade in position I is a maximum. whereas that of the blade in position IX is equal to zero, or a minimum. In other words, whenever a blade completes one whole revolution about the center of the propeller as a whole, its relative velocity with respect to the fluid stream increases from zero in position IX tov f "-1 so.

a maximum in position I, then decreases medium and the blades as they move through the medium. That is, supposing the translational velocity and the peripheral velocity be equall in magnitude and the thickness ot the blade be assumed zero, or be assumed infinitely small, there would be no exchange of energy from the medium to the rotating blades or vice versa.

This new discovery and recognition of thc condition for no interaction between the blades and the fluid medium is important and fundamental as the startin point in developin the relationships whio will render possib e the working out hereinafter of a mechanism of the type of this invention which will operate successfully aerodynamanifestly, from the geometry of the linesshown as velocity vectors, all the resultant velocity lines of the blades form angles with the axis 39-40 of symmetry of the blades which coincide with the angles -formled with said axis by the cords of said blades, that is, there is a condition of sym-` metry .existing with respect to resulting velocity vectorsof blades occupfy'ing similar positions on opposite sides o said axis. This condition of symmetr of the opposing velocity vectors of the bla es coincides with the condition of mechanical symmetry of the blade cords for the situation assumed in Fig. 8. It is important to note that if the velocity vectors' be extended (see dotted lines) these extensions would pass through one common point on the intersection of the axis of symlmetry, and the blade orbit. This point is in the axis of the blade in position Fig. 8. One one side of the axis of symmetry the velocity vectors point away from the axis in position I, whereas on. the other side all Vectors point to the axis in position I.

Now assuming that the peripheral velocity of the blades is greater by fifty per cent than thevelocity of translation (Fi 9), the resultant velocity of the blades sti.l varies from a maximum at position I to a minmium at .position IX, said minm-ium atv position IX being equal to the difference between the two velocities assumed. The resulting velocity vectors have a difference in direction from that of the cords so that an angle alpha is formed. This angle alpha, aerodynamically called the angle of incidence, is responsible for forces acting upon the blade which will be shown inmagnitude as well as direction in Fig. l0. It is seen that this angle alpha depends in magnitude upon the magnitude of the difference between translational and peripheral velocit of the blades. However, the influence of tie mag- -cient aerofoi requires the angle of incidence to be not greater'thanA eighteen derees and the maximum eiiioiency point lies 1n the neighborhood of iive to five and one half de rees for ordinary sha es. The

magnitu e of said angle for all b ades outside said lower quadrant is less than eight. een degrees, i. e. lies Well Within said eiiicient limits. The blades in lowermost quadrant above mentioned working under an angle alpha which is. greater than eighteen degrees 1n magnitude, representing amaximum of ninety degrees at the position IX,

are operating at a velocity which is a minimum for the cycle. Hence, although the langleofincidence falls into the range of ineiiiciency aerodynamically the proportion of the influence of these blades due to said small velocity is negligible in so far as their operation is concerned during the complete cycle. Particularly is this true' since the effect of a blade in developing lift and drag forces is proportional to the square of the velocity, and,therefore, the disadvantaveous effect of the blades in the lower quadrant in comparison to the eii'ect of the remaining blades is small and far out of proportion to thesimple ratio of not only their numbers but also as regards the forces which they develop. The resultant velocity vec-v tors do not, as in Fig-8, coincide with the cords of the blade and intersect in one common axis, but pairs of said vectors intersect at points outside of the orbit, however, still located on the axis of symmetry, the said Vectors of the blades in similar positions on opposite sides ofthe axis 39--40 in the lowermost uadrant meetin Iin said. axis in points be ow position I while the remaining vectors meeting said axis in points above position I. Thus, there is discovered and disclosed this condition of symmetry of the resultant velocitieseven when the velocities of translation and rotation are different in ma itude.

arrying the investigation of vectorial relationship, as shown in Fig 9, to extreme differences of velocity, assuming for instance the velocity of translation equal to Zero, a greater angle alpha, than is shown in the drawing, will result and theoretically i called the burble point.

the efficiency of the vwheel impaired to the extent in which the number of blades operating at an angle of more than eighteen degrees is increased. This condition of Great differences in translational and rotational velocity does however, not exist in ordinary propeller operation. As soon as the blades begin to move in thei'r orbit, the result is movement of the medium and the difference between the velocities of movement will in practice be even smaller than shown diagrammatically in the sketch y because the rotational velocity will immediately tend to make the velocity of the medium approach the rotational velocity, when the propeller is operated as a generator and when the propeller is operated as a motor the peripheral velocity will increase to approach the velocity of translation of the fluid medium. In either case the above is true in a device embodying my invention whether the velocities be great or small.

Parenthetically, be it noted: If a blade moves through a flu-id medium in a direction so that the cord of the blade is angularly inclined to the direction of the impinging fluid medium, it experiences a force act-ion tending to displace they blade in a direction at right angles to its move-- ment. This force is called lift and designated herein as L. At the same time the force of retardation will come into play upon the blade which acts naturally in a direction opposite to the direction of movement of the blade. This force is aerodynamically known as the drag of the blade and designated herein as D. IVhen the angle of incidence is zero, for blades which are symmetrical about their cord, lift is Zero, and when the angle of incidence exceeds the limit of eighteen degrees, the lifting force decreases, this phenomenon being evidenced by eddy currents which develop on the side of the blade away from thel side facing the medium. The point where eddying currents are developed is lFor maximum aerodynamic performance eiiiciency as before indicated, the blade should move so that the lfurble point is avoided and that the ratio of the lift force to the drag forcel is a maximum.' Furthermore, the exact magnitude of the angle of incidence yielding a maxim-um performance eiciency also depends upon the shape of the blade.

In Fig. 10 is shown the resulting forces produced by the interaction of the blades and the medium. These forces are indicated by heavy black lines designated as F and represent the resultant of both lift and drag, the process of obtaining said resultant as `respects each blade being detailed for blade in position IV. Said lift and drag forces are computed from commonly used laerodynamic data compiled from performance tests f flut plates in the fluid stream. The condition of movement of the blade as described in Fig. l0 is exactly the same as shown in Fig. 9. but. for the sake of avoiding confusion, the resulting forces are not shown in Fig. 9 butl are given in Fig. 10, whereas the vectorial combinations of velocities are omitted in Fig. 10. The resulting forces upon the blades. they travel over the orbit in the performance of one cycle. are seen to vary from zero in position I. rising to a gradual maximum over positions IV and V, declining toa very small force at position IX, rising to a maximum over positions XIII and XIV and coming back to zero at I. All forces have been resolved into their vertical and horizontal components represented by dotted lines, designated Fv and Fh respectively, in order to show graphically the contribution of each blade vertically directed and horizontally directed to the total force action on the propeller as a whole, designated Fr, the same being drawn to one tenth the scale of the individual forces F in order to bring this vector within they limits of the diagram.

- Fig. 10 reveals the remarkable factthat all resultant forces (heavy lines marked F) can be thought to operate on one point of the blade orbit (position IX), or the force vectors, if extended, intersect in one common point, the forces operating away from this point on one side of the axis of symmetry, whereas they operate towards this point on the other side of the axis of symmetry. Therefore, from geometrical relations it is evident that all forces which result from the interaction of the blades and the medium act in a direction at right angles to the cords of said blades when we assume that the blade is concentrated in its axis. As stated the force vectors are computed from commonly used test data and since such data produce harmonious results for nearly all the blades, any discrepancies which may occur, as they do in the case of blades in position II and XVI, may for present purposes bey charged to inaccuracy of the test data compiled for and XVI.

An important feature of my invention from the standpoint of designing propellers for practical use resides in this discovery that the forces developed by the blades, when the rotation'of the blades on their its associated bevel gears and shafts to shift the mechanical axis of symmetry, the direction of the resultant forces is controlled, the full significance of which w111 appear in the discussion. of the situation illustrated in diagram, Fig. 11, where it will develop that said control determines not only the direction but the magnitude of said forces.

Comparing the axis of the propeller as a whole with the crankshaft of an engine and the bladeaxis in position IX with the crank pin, we have at all times during the revolution of the shaft a system of forces pushing against said crank pin von one side, and on the other side a similar system of forces pulling on that pin, constituting an ever acting turning moment about the axis of the crankshaft. This turning momentis opposed to the aumed direction of rotation of the propeller as indicated by arrow above figure, and tends to retard the orbit velocity of the blades. Therefore, in order to render the peripheral velocity of the blades in magnitude greater than the translational velocity of the propeller in the medium, a turning eiort must be applied to the rope-ller equal to. the turning effort which arises automatically in opposite direction by virtue vof the interaction of the blades and the mediu'm.

This demonstrates the principle of mechanical motion as fsetforth in Newtons laws that:` If a body be in motion, force is required. to change the magnitude and direction of movement of that body, resulting in an'exchangeofenergy from the outside medium ytothebody'or vice versa. In Fig.

S-itjwasdemonstrated that there could not Q .be"anyiiforcection between blades and me- '40 jas the trans dium'if the eripheral' velocity was. the same y liatonal velocity of the' medium. "Howevemgi'fthisbalance is destroyed, me-' lchanic'al-energymust beapplied to maintain this'. unbalance"of-velocities, orso far it has v.been lde moI ifstrajted that-:in order tol accelerate Y 1 the.` blades s'u'ch 'thatithe peripheral velocity r s isv greater than'the'translationalvelocity, .en-

"'siip'plie'dto overcome the torque Waals. rectio'n ofthe/movement.,- v

Aanalysis so 'far tliatthel horizontal movement of the med'ium-,throughithe propeller'was in -a direction at-'right an les tothe axis of symmetry ofthe blades. i s a 'consequence of this-assumption, it 'results geometrically that the force 'vectors'A are equal in -magnitude on blades equally distant or grouped symmetrically about the axis of symmetry, that is,

the resultant force on blade II is equal to that on blade XVI, that on III equal to XV, et cetera, i. e. the forces are equal upon members constituting a given pair of blades.

However, the direction of force as resfects a given pair of blades is in opposite irec- "videin consequence the maximum lift.

nce 1 set 'jup' in the opposite4 d ition with respect to their vertical componente, whereas the direction coincides'for the horizontal components. rIfhe force combination on the propeller'as a whole results therefore, in a cancellation of the verticai components on one side with the vertical components on the other side of the axis of symmetry and an addition of the horizontal components on one side to the horizontal components on the other side. The final resultant force action Fr, drawn to one-tenth scale, upon the propeller as a whole is a force coincident with the direction of the movement of the propeller as a whole. The discovery of these results constitutes another important step in developin my invention.

The analysis so far has been based on the assumption that the axis of symmetry of the blades is at right angles to the direction ,of the movement of the medium. If this axis of symmetry is displaced from the position shown in Fig. 10, an angle beta is formed. This displacement is shown in 11. The assumed velocities are the same as shown in Fig. 10, that is, the eripheral velocity is fifty per cent greater t an the translational' `the blade in position I coincides with its velocity vector, resultin in zero lift and drag, Whereas, Fig. 11 s ows that an angle is now formed between the cord ofthe blade in position I and its velocity vector, that is fthe velocity of this blade which is greater than all the others is now utilized to rohe aerodynamical effect is not as before, a resultant force in a direction of movement of 'the medium, but an eiort in `that direction combined with an effort at right angles to it. Or the result on the propeller as a whole is notxonly a push in the direction of its movement through the medium but also a vertical force of great magnitude herein designated total vertical force (Fv total). Now, it is apparent that if mechanically the position of 'the axis of symmetry is controllable, the forces resulting from the rotation of the propeller in the medium may at will be changed from a force acting purely in the direction ofthe movement of thepropeller in the medium to a force acting purely at right angles to the movement or any force in. any direction. Fig. 11 'also shows that the force lines on all blades if extended will intersect or nearly so in one common point/on the axis of symmetry, o posite to the point on 'which the blade cords lic.

are trained. However. the systems of forces on opposite sides ofthe axis of symmetry Aare not equal in magnitude as in Fig. 10,

vmarked Fr in Fig. 11 is shown to 1/10 the scale to which the individual blade forces F are drawn as in Fig. 1() in order to bring this vector Within the limits of the diagram.

In diagram Fig. 12. it is assumed that'the peripheral velocity is less than the velocity of translation of the medium. For this condition the velocity vectors are shown to form an angle of incidence on the side of the blade cord. opposite to that shown in Fig. 10, and thus the forces resulting, F ig. 13 constitute a vturning moment in the same direction as the motion of the blades in the orbit. That is, the forces now tend, instead of retarding the motion of rotation of the blades, to accelerate that motion. In other Words, if the propeller be located in a medium, the translational velocity of Which is the same as the rotational velocity of the blades, the unbal- -ancing of these velocities in the direction of increasing the rotational velocity of the blades, implies the supply of energy to the propeller to counteract the turning moment of retardation; whereas, any attempt of reducing the speed of the propeller so as to decrease the rotational velocity of the blades would, of course, imply the Withdrawal of energy through the propeller from the moving medium, and an automatic recovery of tbe velocity balance will result as soon as Withdrawal of energy from the medium ceases. The tendency of the resulting forces to constituteturning moments in a direction depending upon Withdrawal or supply of energy from or to the movin propeller implies an ideal adaptation o' this device to motor o1; generator action, the former refleeting Windmill operation, the latter propeller operation. The Windmill absorbs the kinetic energy ofl the moving fluid medium converting the translational motion of the fluid medium into motion of rotation and generator action will change the motion of rotation of the device into motion et' translation of the fluid medium. Therefore, if the device embodying my invention be placed in a stream of Huid medium. the result will be rotation of the device about its axis and the mechanical energy vvithdrawr: irc-m it will be in proportion to the square of the velocity of the stream of the fluid medium and proportional to the mass of the fluid acted upon. Vice versa, if the device be placed in a fluid and rotated by supplying to it mechanical energy, the result will be a stream entering the device on one side of the axis ot' symmetry and issuing from it on the opposite side, the velocity of the stream being nearly equal to the velocity of the blade in its orbit and the kinetic energy of movement of the fluid being nearly equal to the mechanical energy supplied to the device whether said velocities be great or small.

So far no mention has been made ofthe relative dimensions or proportions of the moving parts of the device so that no consideration of the satellite velocity of points in the cord outside the axis of the blade has been made. The blade in previous discusn sions has been considered as a body of only one dimension, that is, the blade Was assumed to be 'concentrated in its axis and the velocity vector represented t-he movement of this axis only. If We more closely analyze the movement of a blade of iven Width, as is done in Figures 14 and 15, it will be found that only one point along the cord of the blade will move in a circular orbit. This point constitutes the axis of rotation ofthe blade and Will be called P. All other points along the cord possess (a) the peripheral velocity about the axis 30 and (b) the satellite velocity about the axis of the blade Pc.

Manifestly, a blade, contrary to the assumptions (namely that the blade is concentrated in the axis of the blade) on Which said analysis is based, must in the realm of reality, i. e. actual concrete embodiment, have proportions. The all important question then remains whether it is possible to embody in concrete form in a propeller, blades which will operate in a manner to give the very favorable results reached in the analysis so far developed.- What width, if any, is permissible'to the blade and will still develop forces having 'the characteristics of those theoretically produced in the above analysis; again What thickness, if any, is permissible to the blade without destroying its proper. action for attaining said result-s, and nally what form must the blade have to least interfere With the principles deduced by the analysis so far developed? In Figures 14 and 15, a device is diagrammatically illustrated wherein the number of blades, has. been chosen as eight and the width of the blades assumed to be such as to ive the possible'maximum of blade area istributed along the blade orbit or the propeller. The proportion of 'width of blade to diameter of orbit is three vto eight. The velocity vectors are most clearly depicted in position IV of Fig. 111 and for that reason that particular position will be chosen 'for description.

The direction and magnitude of the forces developed by the individual blades having said proportions requires determina-tion 

